Rotary furnace with rotatable chamber



6, 1968 HISAYOSHI MAEDA 3,395,904

ROTARY FURNACE WITH ROTATABLE CHAMBER Filed July 1, 1966 3 Sheets-Sheet1 F l Di /0 K i 1 n i 1 I 1m is, \m; 11

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ROTARY FURNACE WITH ROTATABLE CHAMBER Filed July 1, 1966 5 Sheets-Sheet2 HISAYOSQIIVMIQQA BY M, WM

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ROTARY FURNACE WITH ROTATABLE CHAMBER Filed July 1, 1966 3 SheetsSheet 3INVVENTOR. BY M ATTORA/EKS 6 all] HisAmsH/ MAEDA 8k u h. .ai

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ABSTRACT OF THE DISCLOSURE A rotary furnace with rotatable chamberrotatably supported by means of circular rail and wheels forpredetermined periodic rotation in conjunction with the operation ofcharging and discharging the pieces treated, and the said chamber beingdefined by a domed ceiling and a hearth and the ceiling is provided atthe center thereof with means for jetting the flame into the chamher,and the hearth has beneath the said flame jetting means a batlle platefor permitting turning the jetting flame from the ceiling along theshape of top surface of the baffle plate for diffusing the flame inpredetermined directions for various predetermined heat-treatments.

This invention relates to a horizontal hearth type rotary furnace inwhich the entire heating chamber of the furnace is rotatable instead ofjust furnace hearth.

In the conventional rotating type furnace that heats a large quantity ofmetallic pieces on a rotating hearth,

the rotating hearth is disposed in a fixed furnace body,

and the pieces to be heated are charged onto and discharged from therotating hearth through a charging opening provided in a portion of thefixed furnace body. Owing to the extreme thermal expansion of therotating hearth because of the heating thereof during operation,

it is the practice in order to overcome any difliculty in rotating thehearth due to sticking of the rotating hearth to the fixed furnace body,even when the rotating hearth expands because of heating thereof duringoperation of the furnace, to construct the rotating hearth with arelatively large clearance between the periphery of the rotating hearthand the opposed peripheral face of the fixed furnace body. However,oxides (scale or scraps) or portions of the pieces to be heated getcaught in this clearance, and this is liable to damage the hearth orblock rotation thereof. Such a furnace, because of this construction, isextremely poor in heating efficiency, and numerous defects occur duringpractical use thereof, such as in charging and discharging of pieces tobe heated, inpection, repair and the like.

It is an object of the present invention to provide a rotary furnace inwhich the heating chamber is defined by a hearth and a domed ceiling inthe furnace body, which body is supported so as to rotate freely onseveral wheels on a circular rail. Exhaust openings which communicatewith the air outside the furnace are provided in the periphery of areverberatory block which projects upwardly from the hearth opposite astationary heavy oil burner that is directed into the heating chamberfrom the center of the doomed ceiling. Charging openings for the heatingchamber are provided at certain intervals around the periphery of thefurnace body. A door is provided for each charging opening which closesthe charging opening and the door opens only when the charging openingcoincides with the handling stand provided at the side of the furnacebody during the intermittent rotation of the furnace body.

It is a further object of the invention to provide a structure whichmakes the rotation of the furnace body smooth, as well as makingpossible the heating of a large States Patent 3,395,964 Patented Aug. 6,1968 ice quantity of pieces uniformly and with a high efliciency bymeans of a single heavy oil burner.

The invention will now be described in connection with the accompanyingdrawings, in which:

FIG. 1 is a front elevation view of the furnace according to the presentinvention;

FIG. 2 is a sectional plan view taken on line 22 of FIG. 1;

FIG. 3 is a vertical sectional view taken on line 3-3 of FIG. 1;

FIG. 4 is a view of a portion of the furnace as shown in FIG. 3 showingthe charging and discharging door open;

FIG. 5 is a sectional view taken on line 5-5 of FIG. 4;

FIGS. 6 and 7 are plan and side elevational views, respectively, of thereverberatory block; and

FIG. 8 is a perspective view of half the reverberatory block of FIGS. 6and 7.

The furnace to be described in connection with the drawings is used forheating pieces to be forced, such as pieces of round steel bar. Thefurnace comprises a rotatable furnace body 1 which has wheels 2 mountedthereon which run on a circular rail 3 beneath the furnace. The bottomof the furnace is in rotatable and airtight relationship with a mainpedestal 4. A heating chamber 6 is defined by a domed ceiling 5 and ahearth 11. A tapered hole 7 is provided in the top of the domed ceiling5, in which hole is fitted a burner tile 8. The tile 8 is fitted in thetapered hole 7 so that it can be easily positioned and removedtherefrom. In a burner hole 9 in the tile 8 is an oil burner 10 forburning heavy oil, the burner 10 being stationary with respect to thefurnace body 1 and mounted on an oil supply means (not shown) outsidethe furnace body 1. The burner 10 directs a flame downwardly into thheinterior of the chamber 6. At the center of the hearth 11 is aprojection or pedestal 13 having a baffle plate 12 on the top thereofopposite the burner hole 9. Exhaust openings 14 extend radially out ofthe pedestal 13, opening out of the peripheral surface thereof, and atthe inner ends thereof they are in communication with an exhaust bore 15extending downwardly through the main pedestal 4 with which the fgrnacebody 1 turns in substantially airtight relation- 5 1p.

The top of the baffle plate 12 is shaped so as to reverberate the flamefrom the oil burner 10 which jets downwardly through the burner hole 9,and to diifuse the flame widely and toward the ceiling 5 of the heatingchamber 6, for example in the pattern shown in FIG. 3 of the drawings.The projection on the bafile plate should have the same general shape asthe peripheral shape of the baffle plate 12. For example, when the plateis hexagonal, as shown in FIG. 2, in order to conform to the pattern ofthe heating areas in the furnace, the projection should have a hexagonalshaped pyramid on the top thereof, as shown more clearly in FIGS. 68, inorder to diffuse the flame uniformly over the widest possible area ofthe chamber. When the plate 12 is circular, the projection can beconical. Moreover, in order to make the manufacture, mounting, andrepair and replacement easy and economical, the plate 12 can be made ina plurality of segments, as shown in FIGS. 6-8.

An appropriate number of charging and discharging openings 16 areprovided at spaced intervals along the chamber wall. In the embodimentshown, there are six such openings, one in each of the six sides of thehexagonal chamber. Each of the openings is provided with a door member18 mounted on lifting rods 17 which in turn are mounted so as to bemovable up and down on the outside of the furnace body 1. On the bottomperiphery of the furnace body 1 is mounted a ring gear 19 in mesh with adriving pinion driven in turn by a motor 22, such. as an electric motor,on the base through a speed reduction gear 21.

In order to provide for intermittent rotation of the furnace body 1around its central axis on the track 3, a limit switch. can be providedwhich is actuated by a cam head 24 which extends outwardly from the ringgear 19, there being one cam head 24 for each opening 16 and door 18.Thus, when the cam head 24 strikes the limit switch 25, the electricmotor 22 is stopped for a certain period of time with the opening 16corresponding to the particular cam head at a handling stand 23 at theside of the rotating body.

At a point coinciding with the position of the handling stand 23 is ameans for lifting a door 18, which means comprises a support head 27 onwhich the lower ends of the rod 17 rest, and a motive means for movingsaid support head up and down, such as a fluid piston-cylinder liftingmechanism 26. The lifting mechanism 26 can be controlled eithermanually, or can be caused to operate by means of the limit switch whichis actuated when the housing 1 reaches the appropriate position duringits rotation. The length of time that the door 18 will remain raised canbe controlled manually or by means of a timer switch (not shown)connected in the operating circuit for the lifting mechanism 26.Likewise, the motor 22 can be restarted manually when the door 18 hasbeen lowered, or it can be started automatically by limit switch 29which is engaged by a projection 28 on the movable member of the liftingmechanism 26. Thus, when the door 18 has been completely closed, afterthe heated pieces have been discharged and unheated pieces chargedthrough the opening 16, the rotation of the furnace body 1 is resumed.

The handling stand 23, as shown in the drawings, has a receiving table23a on a level slightly lower than bottom surface of the opening 18, anda delivery table 23b on a level slightly higher than the bottom surfaceof the opening 18. A separating flange is provided between the receivingtable 23a and the delivery table 23b in order to hold the unheatedpieces in place while heated pieces are removed from the furnace andconveyed away on a level or slightly downwardly inclined forwardingtable 23c adjacent the receiving table 23a. A feeding table 23d isattached to the delivery table 23b, and is inclined downwardly towardthe delivery table 23b for feeding pieces to be heated eitherautomatically or semi-automatically.

It is of course possible to provide additional handling stands ifdesired, and to provide door lifting means thereat, and to arrange todeliver unheated pieces to the furnace at one such stand and removeheated pieces at another such stand.

The hearth 11 in the heating chamber 6 is constructed of fire bricks orother fire resisting materials and is constructed so that the piecesthereof can be passed into and out of the chamber 6 through the openings16 or the fitting hole 7, and as with the bafiie plate 12, it isdesirable to construct the hearth in pieces so that it can be readilyreplaced if it is damaged by a violent blow or from the heat. The sixcharging openings are provided so that access can be gained to all sidesof the hexagonal bafiie plate 12 and the pedestal 13, as the drawingshows. Hexagonal heating chambers are formed between the pedestal 13 andthe charging openings 16, and the hexagonal hearths thereof areconstructed so as to be separable into a plurality of pieces so thatthey can be passed in and out of openings 16 and hole 7 together withthe pieces of the baflie plate.

In operation, the major portion of the flame from the oil burner 10 forthe heavy oil which is directed downwardly from the burner hole 9 in thecenter of the burner tile 8 in the central portion of the ceiling of thefurnace body, strikes the baffle plate 12 and heats it red hot. Inaddition, the flame reverberates and is diffused, by virtue of thepolygonal pyramidal or conical projection on the top face of the baflleplate 12, uniformly over a wide area toward the ceiling and heats theceiling red hot as well. After heating the entire heating chamber to ahigh temperature, it is exhausted through the exhaust openings 14 andthe exhaust passage 15.

The pieces to be heated are laid on the hearth 11 of the heating chamber6 after having been charged through the charging opening 16, and areheated uniformly by being exposed to the high temperature in the heatingchamber. When the piece to be heated have been charged into the heatingchamber through the charging opening 16 and the door 18 is closed,either by a timer switch or a manually actuated switch, the projection28 strikes the limit switch 29 and the electric motor 22 is operated.The furnace body 1 rotates while the action of the fixed burner 10continues as described above. The furnace body 1 stops when a cam head24 corresponding to the next charging and discharging opening 16 andprovided on the side of the furnace body strikes and actuates the limitswitch 25 and stops the operation of the electric motor 22. Since thestopping position of the furnace body 1 is determined so that the nextopening 16 coincides with the handling stand 23, the lifting rods 17that control the door 18 for the charging opening stop right above thesupporter head 27 on the fluid hoist 26. At the same time as the furnacebody stops due to the actuation of the limit switch 25, the fluid thatactuates the fluid lifting mechanism 26 is caused to flow.Alternatively, a pushbutton electric switch can be provided to bemanually actuated to accomplish the same result. The fluid liftingmechanism is lifted, the lifting rods 17 positioned on the supporterhead 27 are lifted, and the door 18 connected to the rods is lifted. Itwill be seen that it is possible to open only the charging opening 16that is positioned at the handling stand 23. There is no means to liftthe rods 17 controlling the doors 18 of the other openrngs.

Thus, the pieces a to be heated in the heating chamber 6 that arecharged into the chamber through the charging opening are exposed to ahigh temperature and are heated uniformly for the period of time ittakes the furnace body to rotate intermittently through the angle towhere the pieces are discharged. In the construction shown in thedrawing, the rotation is through 360. The heating temperature and theintermittent rotating speed of the furnace body and the number ofhandling stands can be selected so as to keep the pieces constantly atthe optimum temperature for the purposes of the treatments to follow theheating, such as forging and hardening, and also depending on the shape,composition, volume, etc. of the pieces.

The heated pieces a that are in the heating chamber which is open at thehandling stand 23 must be transferred rapidly away from the chargingopening, and in the structure of the invention as shown in the drawingsthis is accomplished by the provision of the receiving table 23a beingon a level slightly below the bottom edge of the charging opening. Afterthe pieces which have been heated are removed from the furnace, they aretransferred to their next destination by the forwarding table 231:, or aconveyor or the like adjacent the receiving table 23a. Since theunheated pieces a are charged into the heating chamber through the samecharging opening through which the heated pieces have been removed fromthe delivery table 2312 which is on a level slightly higher than thebottom edge of the charging opening and the pieces a are suppliedautomatically from the inclined feeding table 23d, the operation ofremoving heated pieces and charging unheated pieces through the chargingopening is very rapid and relatively easy.

After the heated pieces a have been removed from the furnace and theunheated pieces a charged in their place, the fluid supply to the fluidlifting mechanism 26 is again caused to flow, either by a pre-set timermeans or manually, so that the door 18 is lowered to close the chargingopening and simultaneously the limit switch 29 is actuated by theprojection 28 to operate the electric motor 22 so as to rotate thefurnace. When the next charging opening 16 reaches the position in frontof the handling stand 23, the motor 22 is again stopped and the abovedescribed operation is repeated.

Because none of the rods 17 other than the rods which are at thehandling stand 23 will be above the supporting head 27 on the fluidlifting mechanism 26, none of the other doors will be opened at the sametime the door at the handling stand 23 is opened, and it is thereforepossible to prevent the temperature of the heating chamher from droppingunduly and to make the heating of the pieces even because there can beno accidental opening of any of the other doors. The thermal etficiencyof the furnace will likewise be increased.

Moreover, with the rotary furnace of the invention, because the furnacebody 1 is freely rotatable on the Wheels 2 on the circular rail 3, andbecause during the intermittent rotation of the furnace, the mainpedestal 4 and the furnace body 1 are maintained in substantiallyairtight relationship so that air can enter the furnace chamber 6 onlythrough top and peripheral openings thereof and can be withdrawn onlythrough the exhaust openings 14 and the exhaust passage 15, the interiorof the chamber 6 is heated throughout to a substantially uniform hightemperature by the flame directed through the opening 9 at the top ofthe furnace chamber from the single burner 10. It is easy to rotate thefurnace smoothly and intermittently and at the desired speed and stillmaintain this heating. Consequently, a large quantity of pieces can beheated to a certain temperature continuously, uniformly, and equally andwith a large degree of precision Within a relatively small workingspace. The efficiency of the operation is thereby increased and inaddition the subsequent treatments of the metal pieces, such as forging,hardening, and the like, can be performed so as to produce uniformquality products with consistency. The ability consistently to heat thepieces evenly to a certain temperature for a certain time without damageto the pieces makes it possible to prevent adverse effects due to faultyheating on the pieces during subsequent treatments. This is particularlytrue since the intermittent rotation of the furnace body and the openingand closing actions of the door which is at the handling stand can beinterconnected so as to be performed automatically or semi-automaticallyso that the heating is to the optimum temperature for the particularshapes, nature of the material and the size of the pieces and the usesto which they are to be put. Moreover, the apparatus can be used forlong periods of time without it being necessary to shut it down, andwhen repairs are necessary, the various segments of the different partscan be readily replaced.

What is claimed is:

1. In a rotary furnace of the type in which the entire heating chamberof the furnace is rotated, the combination comprising a heating chamberhaving a hearth and a domed ceiling, a circular rail beneath saidheating chamber, a plurality of wheels on said heating chamber andrunning on said circular rail, drive means coupled with said heatingchamber for driving it in rotational movement along said circular railand comprising a ring gear on said furnace, a motor having a pinion gearengaged with said ring gear, a plurality of cam heads on said chambercorresponding in number to the number of charging openings, a limitswitch adjacent the rotational path of said cam heads and connected tosaid motor, said cam heads being positioned to engage and actuate saidlimit switch when the corresponding charging opening is at said handlingstand, said domed ceiling having an aperture at the top thereof, aburner directed into said chamber through said aperture, fixed burnermounting means above said chamber .and unconnected therewith on whichsaid burner is mounted, a baffle plate projecting upwardly from thehearth of said furnace beneath said aperture, said furnace havingexhaust openings beneath said baflie plate and an exhaust flue extendingdownwardly beneath said baflie plate into which said exhaust openingsopen, a fixed exhaust flue beneath said chamber with which saiddownwardly extending exhaust flue is in rotational sealing engagement,said chamber having a plurality of charging openings around theperiphery thereof, doors over each charging opening, and at least onehandling stand adjacent the periphery of said chamber with which thecharging openings are successively aligned when the furnace chamber isrotated.

2. The combination as claimed in claim 1 in which said baffle plate hasa polygonal periphery with sides corresponding in number to the numberof charging openings through which the treating pieces are charged anddischarged for the eflicient reverberation of the flame for goodheat-treatment.

3. The combination as claimed in claim 2 in which said baffle plate hasat least three sides and the inner peripheral wall of the chamberextends radially inwardly into the space between adjacent treating piececharging openings for improvingthe flame reverberation effect.

4. The combination as claimed in claim 2 in which said baffle plate hasa pyramidal projection on the top surface thereof having a number ofsides corresponding to the number of sides in the periphery thereof sothat the reverberation of the flame to the treating pieces can beefficiently performed.

5. The combination as claimed in claim 2 in which the exhaust openingscorrespond in number to the number of sides in the periphery of thebaflle plate.

6. The combination as claimed in claim 1 in which said doors movevertically, and further comprising lifting means for said doors, saidlifting means comprising at least one lifting rod on each door, andhydraulic hoist means at said handling stand engageable with the liftingrod on the door at said stand for lifting the door so as to open thechanging opening.

7. The combination as claimed in claim 1 in which said handling standcomprises a receiving table extending across at least parts of thecharging opening and being at a level slightly below the level of thebottom of the charging opening, and a delivery t-able extending acrossthe remainder of the charging opening and being at a level slightlyhigher than the bottom of the charging opening, and a separating flangebetween said delivery table and said receiving table and projectingupwardly from the level of said delivery table to prevent pieces to becharged from moving from the delivery table to the receiving table.

References Cited UNITED STATES PATENTS 452,007 5/1891 Sternbergh 263-71,280,889 10/1918 Spang 263-7 2,413,228 12/1946 Hepburn et a1. 2637FREDERICK L. MATTESON, JR., Primary Examiner.

JOHN J. CAMBY, Assistant Examiner.

